A Taiwan patent No. M383651 disclosed a screw, which comprises a head and a shank extended from one side of the head and having a drill bit at the free end thereof. The shank includes a first thread neighboring the head and a second thread neighboring the drill bit. A non-threaded section is formed between the first thread and the second thread. The pitch of the first thread is smaller than the pitch of the second thread. Each circle of the second thread includes a plurality of breaking teeth for debris removal. The drill bit includes two cutting edges with the included angle therebetween being an acute angle. The conventional screw can fix a plurality of boards together and can decease the screwing stress lest the boards crack.
The non-threaded section of the conventional screw is free of threads and lacks sufficient force to bite the boards tight. Thus, the screwed boards may be joined insecurely and shake. Besides, the like screws have a smooth and round surface, which may make the operator unable to hold it stably or position it precisely and thus result in inaccurate screwing. Therefore, the conventional technology still has room to improve.